diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 56a70df5b84..19b21be73e7 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -8,6 +8,7 @@ Yii Framework 2 Change Log
 - Bug #4889: Application was getting into redirect loop when user wasn't allowed accessing login page. Now shows 403 (samdark)
 - Bug #5402: Debugger was not loading when there were closures in asset classes (samdark)
 - Bug #5452: Errors occurring after the response is sent are not displayed (qiangxue) 
+- Bug #5521: Fixed `yii\console\controllers\AssetController` breaks CSS URLs, which start from '/' (klimov-paul)
 - Bug #5570: `yii\bootstrap\Tabs` would throw an exception if `content` is not set for one of its `items` (RomeroMsk)
 - Bug #5584: `yii\rbac\DbRbacManager` should not delete items when deleting a rule on a database not supporting cascade update (mdmunir)
 - Bug #5601: Simple conditions in Query::where() and ActiveQuery::where() did not allow `yii\db\Expression` to be used as the value (cebe, stevekr)
diff --git a/framework/console/controllers/AssetController.php b/framework/console/controllers/AssetController.php
index fb1dc786348..28c568b7086 100644
--- a/framework/console/controllers/AssetController.php
+++ b/framework/console/controllers/AssetController.php
@@ -565,7 +565,7 @@ protected function adjustCssUrl($cssContent, $inputFilePath, $outputFilePath)
             $fullMatch = $matches[0];
             $inputUrl = $matches[1];
 
-            if (preg_match('/^https?:\/\//is', $inputUrl) || preg_match('/^data:/is', $inputUrl)) {
+            if (strpos($inputUrl, '/') === 0 || preg_match('/^https?:\/\//is', $inputUrl) || preg_match('/^data:/is', $inputUrl)) {
                 return $fullMatch;
             }
 
diff --git a/tests/unit/framework/console/controllers/AssetControllerTest.php b/tests/unit/framework/console/controllers/AssetControllerTest.php
index e5b7b4fd167..0b1ae94e667 100644
--- a/tests/unit/framework/console/controllers/AssetControllerTest.php
+++ b/tests/unit/framework/console/controllers/AssetControllerTest.php
@@ -386,6 +386,12 @@ public function adjustCssUrlDataProvider()
                 'C:\test\base\path\assets\output',
                 '.published-same-dir-class {background-image: url(../input/published_same_dir.png);}',
             ],
+            [
+                '.static-root-relative-class {background-image: url(\'/images/static_root_relative.png\');}',
+                '/test/base/path/css',
+                '/test/base/path/assets/output',
+                '.static-root-relative-class {background-image: url(\'/images/static_root_relative.png\');}',
+            ],
         ];
     }